Wikipedia says pointillism is a method of painting small dots of different colours, where dots are placed to form a pattern. These patterns form an image. This style was developed in the 1880s and 1890s.

Technique

This technique of painting was pioneered by Paul Signac and Georges Seurat. Small dots of pure colour instead of mixing colours on a palette. The colours are both primary and secondary colours. Dots of these colours were placed close to one another. An entire picture is built this way.

Coloured dots placed at close proximity fuse together when seen with the human eye. The interspersing of white canvas in between the dots increases the contrast of the painting.

Lines look clear and sharp and colours look fused and seamless when seen from a distance due to the way the human eye is able to see the dots from a distance.

Divisionism

Pointillism is an offshoot of Divisionism. Divisionism is the arranging of small dots or patches on a canvas. This was developed off of the impressionist movement.

Divisionism was followed by a number of painters of modern art such as included Henri-Edmond Cross (1856-1910), Henri Matisse (1869-1954), Maximilien Luce (1858-1941), Robert Delaunay (1885-1941), Theo Van Rysselberghe (1862-1926), Jan Toorop (1858-1928), Van Gogh (1853-90), Andre Derain (1880-1954), Jean Metzinger (1883-1956) and Giacomo Balla (1871-1958).

Even Camille Pissarro used pointillism for some of his later work – Gelée blanche, jeune paysanne faisant du feu – that depicts a woman and child making fire. It is said that Camille Pissarro worked on this artwork for six months. Some of his other work as show his interest in this technique.

Divisionism and Pointillism, although ridiculed during their inception, have brought out some of the most beautiful and celebrated pieces of artwork in the post-impressionist era of modern art. An experimental technique that led to a new and innovative way of working with paint and a different way of looking at brushwork, has resulted in giving the art world some of its best masterpieces.